A new photosensory function for simple photoreceptors, the intrinsically photoresponsive neurons of the sea slug Onchidium
Simple photoreceptors, namely intrinsically light-sensitive neurons without microvilli and/or cilia, have long been known to exist in the central ganglia of crayfish, Dryer Drum Bearing Aplysia, Onchidium, and Helix.These simple photoreceptors are not only first-order photosensory cells, but also second-order neurons (interneurons), relaying severa